French lawmakers appealed to their country's highest court on Tuesday to overturn a law that makes it illegal to deny that the mass killing of Armenians by Ottoman Turks nearly a century ago was genocide.
The move raises the possibility that the law, which sparked an angry reaction in Turkey, will be dismissed as unconstitutional.
The legislation, which received final parliamentary approval on January 23, prompted Ankara to cancel all economic, political and military meetings with Paris.
More than 130 French lawmakers from both houses of parliament and across the political divide, who had originally voted against the bill, appealed to the Constitutional Council.
The court has one month to make its decision.
Turkish Prime Minister Tayyip Erdogan, who branded the legislation discriminatory and racist, thanked the lawmakers who opposed it.
On behalf of my country, I am declaring our heartfelt gratitude to the senators and deputies who gave their signatures, he said. I believe they have done what needed to be done.
The lawmakers argued in their appeal that the event was still the subject of historical contention, and therefore the legislation infringed on the freedoms of historians, analysts and others to debate it, ultimately violating the right to free speech.
They insisted their move did not aim to deny the suffering of our compatriots of Armenian origin and of all Armenians across the world.
Last week, Erdogan said Turkey was in a period of patience as it considered what measures to take.
As a member of NATO and the World Trade Organisation, Turkey may be limited in its response by its international obligations. However, newspapers have listed possible measures that Ankara might take against France.
These included recalling its ambassador in Paris and expelling the French ambassador in Ankara, thus reducing diplomatic ties to charge d'affaires level, and closing Turkish airspace and waters to French military aircraft and vessels.
President Nicolas Sarkozy must still ratify the law, a move now on hold pending the court's decision.
Mostly Muslim Turkey accuses Sarkozy of trying to win the votes of 500,000 ethnic Armenians in France in the two-round presidential vote on April 22 and May 6. France's Socialist Party, which has a majority in the upper house, and Sarkozy's UMP party, which put forward the bill, supported the legislation.
Armenia, backed by many historians and parliaments, says about 1.5 million Christian Armenians were killed in what is now eastern Turkey during World War One in a deliberate policy of genocide ordered by the Ottoman government.
The Ottoman empire was dissolved after the end of the war, but successive Turkish governments and the vast majority of Turks feel the charge of genocide is a direct insult to their nation. Ankara argues there was heavy loss of life on both sides during fighting in the area.
French companies in Turkey ... wanted the Constitutional Council to be involved because it's the best solution to calm the Turks, said Dorothee Schmid, head of the Turkish programme at the French Foreign Relations Institute in Paris.
The Turkish government accused the French government of being racist and discriminatory, yet this matter stems from the inability of the Turks to handle the genocide case. Now there is a discussion on it.
France is Turkey's fifth biggest export market and sixth biggest supplier of imports of goods and services, and bilateral trade was $13.5 billion in the first 10 months of last year.
(Reporting By John Irish and Pinar Aydinli in Ankara, Writing by John Irish and Jonathon Burch; Editing by Alessandra Rizzo)